CN106939845A - The control device of internal combustion engine - Google Patents

Abstract

The present invention provides a control device for an internal combustion engine capable of properly controlling the supercharging state and overlap period in a direct injection internal combustion engine having a supercharger with an electric motor and a variable valve action phase mechanism, increasing the output of the internal combustion engine to improve fuel efficiency, and Improved supercharger responsiveness. When performing motor-assisted supercharging control to drive and assist the compressor (123) by the motor (124), such control is performed by increasing the opening degree WGO of the exhaust pressure relief valve (14) and increasing the opening degree of the intake valve. The valve opening period overlaps the valve opening period TCAOVL of the exhaust valve. At the start time of the motor assist supercharging control, the driving torque of the motor (124) is set to the maximum torque TMAX, and the opening degree WGO of the wastegate valve (14) is set to the maximum opening degree VOMAX.

Description

Control devices for internal combustion engines

technical field

The present invention relates to a control device for an internal combustion engine having a supercharger capable of assisting the drive of an electric motor and directly injecting fuel into a combustion chamber, and more particularly to a valve operation capable of changing the operating phase of an intake valve and/or an exhaust valve of the internal combustion engine A control device for an internal combustion engine with a phase variable mechanism.

Background technique

Patent Document 1 shows a control device for an internal combustion engine including a variable valve movement mechanism and a supercharger with an electric motor. When supercharging is performed by operating the electric motor, since the differential pressure between the intake pressure and the exhaust pressure (= intake pressure - exhaust pressure) increases, there is fuel flowing into the combustion chamber and the intake air directly The amount discharged into the exhaust passage (blow-off amount) tends to increase. In order to reduce the blow-off amount, the control device performs an overlap period in which the valve opening period of the intake valve overlaps with the valve opening period of the exhaust valve when the electric motor is operating (when assisting the drive of the supercharger). Shorter control than when the motor is not operating. Thereby, it is possible to prevent the blow-off amount from increasing excessively.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2007-23837

Since the internal combustion engine disclosed in Patent Document 1 is a port-injection internal combustion engine that injects fuel into an intake port, deterioration in fuel efficiency and deterioration in exhaust characteristics are significant due to an increase in the blow-off amount during the overlap period. In contrast, a direct-injection internal combustion engine that injects fuel directly into the combustion chamber can achieve the following effects: the injection timing of fuel can be set from the latter half of the intake stroke to the compression stroke, and in addition, by promoting combustion during the overlap period The scavenging of the final residual gas improves the output of the internal combustion engine and improves fuel efficiency.

Contents of the invention

The present invention has been made in view of this problem, and an object of the present invention is to provide a control device for an internal combustion engine capable of appropriately controlling the supercharging state and the state of supercharging in a direct injection internal combustion engine having a supercharger with an electric motor and a valve operation phase variable mechanism. During the overlap period, the output of the internal combustion engine is increased, the fuel efficiency is improved and the responsiveness of the supercharger is improved.

In order to achieve the above object, the invention described in technical scheme 1 is a control device for an internal combustion engine (1), the internal combustion engine is an internal combustion engine in which fuel is directly injected into a combustion chamber, and the control device has: a supercharger (12); a variable mechanism (20) capable of changing the operating phase of at least one of an intake valve and an exhaust valve of the internal combustion engine; and an exhaust pressure relief valve (14) provided at a In the bypass passage (11) of the turbine, the supercharger (12) has: a turbine (121), which is arranged in the exhaust passage (10) of the internal combustion engine; a compressor (123), which is controlled by the turbine rotationally driven to pressurize the intake air of the internal combustion engine; and an electric motor (124) configured to be able to drive the compressor, the control device of the internal combustion engine (1) is characterized in that it is controlled by the electric motor ( 124) When the compressor (123) is driven and assisted, the opening (WGO) of the exhaust pressure relief valve is increased, and the valve opening period of the intake valve and the valve of the exhaust valve are increased. Open period overlap overlap period (TCAOVL). Here, "increasing the overlapping period" includes increasing the overlapping period from a state greater than "0" and increasing the overlapping period from a state equal to or less than "0" at the time when the compressor drive assistance by the motor is started. Condition.

According to this configuration, when the motor assists in driving the compressor, control is performed such that the opening degree of the wastegate valve is increased, and the overlap between the valve opening period of the intake valve and the valve opening period of the exhaust valve is increased. Overlap period. By increasing the opening of the exhaust relief valve, the increase in exhaust pressure can be minimized when the required load of the internal combustion engine is high, the filling efficiency can be improved, and the ignition timing can be set close to the optimum ignition timing. Time. In addition, by increasing the overlap period, it is possible to promote the removal of residual gas in the combustion chamber, increase the amount of fresh air, avoid knocking, and advance the ignition timing. As a result, the output of the internal combustion engine can be increased to improve fuel efficiency, and the responsiveness of the supercharger can be improved.

The invention according to claim 2 is based on the control device for an internal combustion engine according to claim 1, characterized in that the driving assistance by the electric motor (124) is performed when the rotation speed of the internal combustion engine is low and the internal combustion engine Executed in operating conditions where the intake air pressure is lower than the target boost pressure (POBJ).

When the engine speed is low and the intake pressure is lower than the target supercharging pressure, the electric motor is used to drive and assist, so that the rise of the intake pressure can be accelerated, and the effect of improving the responsiveness of the supercharger and the effect of accelerating the purge can be obtained. .

The invention according to claim 3 is based on the control device for an internal combustion engine according to claim 1 or 2, characterized in that after the drive assist by the electric motor (124) starts, the internal combustion engine When the intake pressure (PB) reaches the target boost pressure (POBJ), the output of the electric motor (124) is reduced and the opening (WGO) of the wastegate valve is reduced.

According to this configuration, after the start of the drive assist by the electric motor, when the intake air pressure reaches a predetermined pressure, control is performed such that the output of the electric motor is reduced and the opening of the wastegate valve is reduced. After a sufficient supercharging pressure (target supercharging pressure) is obtained, the driving assistance by the electric motor is reduced and shifted to supercharging using normal exhaust energy, thereby reducing the electric power for driving the electric motor.

The invention according to claim 4 is based on the control device for an internal combustion engine according to claim 1 or 2, characterized in that a predetermined period of time has elapsed since the start of drive assistance by the electric motor (124). At time (TMASTX), the output of the electric motor (124) is reduced and the opening of the wastegate (WGO) is reduced.

According to this configuration, when a predetermined time elapses from the start of the drive assistance by the electric motor, control is performed such that the output of the electric motor is reduced and the opening of the wastegate valve is reduced. By setting the predetermined time as the time when the intake air pressure reliably reaches the target supercharging pressure, the same effect as that of the invention described in claim 3 can be obtained.

Description of drawings

FIG. 1 is a diagram schematically showing the structure of an internal combustion engine according to an embodiment of the present invention.

Fig. 2 is a block diagram showing the configuration of a control system for the internal combustion engine shown in Fig. 1 .

3 is a diagram showing lift curves of intake valves and exhaust valves for explaining a variable range of valve operating phases of the valve operating phase variable mechanism in FIG. 1 .

4 is a graph showing the relationship between the engine speed (NE), the intake pressure (PB) and the exhaust pressure (PEX) when the throttle valve opening is fully opened.

FIG. 5 is a time chart for explaining the outline of motor assist supercharging control.

6 is a graph showing the relationship between the differential pressure (DP) obtained by subtracting the exhaust pressure (PEX) from the intake pressure (PB) and the overlap period (TCAOVL).

7 is a diagram showing a map used for calculation of valve operation phases (CAIN, CAEX) of intake valves and exhaust valves.

FIG. 8 is a graph showing transition of the output torque (TRQE) when the engine output control corresponding to the demanded torque (TRQD) is performed.

FIG. 9 is a timing chart for explaining that the period during which the intake pressure is higher than the exhaust pressure and the scavenging effect can be obtained is increased by performing motor assist.

FIG. 10 is a flowchart for explaining motor assist supercharging control processing.

Label description

1: internal combustion engine; 2: intake passage; 10: exhaust passage; 11: bypass passage; 12: turbocharger (supercharger); 121: turbine; 123: compressor; 124: motor; 14: exhaust Pressure relief valve; 20: Valve action phase variable mechanism; 21: Intake air pressure sensor; 22: Intake air flow sensor; 23: Engine speed sensor; 24: Throttle sensor; 30: Electronic control unit

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing the structure of an internal combustion engine according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as "engine") 1 is a direct injection engine having four cylinders 6 and injecting fuel directly into the combustion chambers of the cylinders 6. Each cylinder 6 is provided with a fuel injection valve 7, a spark plug 8, and an intake valve and exhaust valves (not shown).

The engine 1 has an intake passage 2 , an exhaust passage 10 , a turbocharger (supercharger) 12 , and a valve operation phase variable mechanism 20 . The intake passage 2 is connected to the surge tank 4 , and the surge tank 4 is connected to the combustion chamber of each cylinder 6 through the intake manifold 5 . An intercooler 3 for cooling pressurized air and a throttle valve 13 are provided in the intake passage 2, and the throttle valve 13 is configured to be drivable by a throttle valve actuator 13a. An intake pressure sensor 21 for detecting the intake pressure PB is provided in the surge tank 4 , and an intake air flow sensor 22 for detecting the intake air flow rate GAIR is provided in the intake passage 2 .

The turbocharger 12 has: a turbine 121 provided in the exhaust passage 9 and rotationally driven by the kinetic energy of the exhaust; a compressor 123 coupled to the turbine 121 via a shaft 122; and a motor (electric motor) 124. It is arranged to be able to drive the shaft 122 in rotation. The compressor 123 is provided in the intake passage 2 and pressurizes (compresses) the air sucked into the engine 1 . Driving assistance of the compressor 123 by the auxiliary turbine 121 is performed by driving the motor 124 .

The valve operation phase variable mechanism 20 is a mechanism for changing the operation phase of the intake valve and the exhaust valve of each cylinder 6 .

A combustion chamber of each cylinder 6 of the engine 1 is connected to an exhaust passage 10 through an exhaust manifold 9 . A bypass passage 11 bypassing the turbine 121 is connected to the exhaust passage 10 , and an exhaust relief valve 14 is provided in the bypass passage 11 , and the exhaust relief valve 14 controls the flow rate of exhaust gas passing through the bypass passage 11 .

2 is a block diagram showing the configuration of a control system for controlling the engine 1. An electronic control unit (hereinafter referred to as "ECU") 30 is connected to the intake air pressure sensor 21 and the intake air flow sensor 22 described above, as well as The engine speed sensor 23 detects the rotational speed NE of the engine 1, the accelerator sensor 24 detects the depression amount (hereinafter referred to as "accelerator pedal operation amount") AP of the accelerator pedal (not shown) of the vehicle driven by the engine 1, and detects the engine speed. A cooling water temperature sensor 25 for the cooling water temperature TW and other sensors not shown are connected, and detection signals of these sensors are supplied to the ECU 30 .

The output side of the ECU 30 and the fuel injection valve 7, the spark plug 8, the motor 124, the exhaust valve 14, the throttle actuator 13a, and the intake valve actuator 201 provided in the valve operation phase variable mechanism 20 It is connected to the actuator 202 for the exhaust valve. The intake valve operation phase CAIN is changed by driving the intake valve actuator 201 , and the exhaust valve operation phase CAEX is changed by driving the exhaust valve actuator 202 .

The ECU 30 has an input circuit, a central processing unit (hereinafter referred to as "CPU"), a storage circuit, and an output circuit, wherein the input circuit has functions of shaping input signal waveforms from various sensors, correcting voltage levels to The storage circuit stores various calculation programs and calculation results executed by the CPU, and the output circuit supplies drive signals to the motor 124 and the like.

The ECU 30 performs fuel injection control by the fuel injection valve 7, ignition control by the spark plug 8, drive assist control of the turbocharger 12 by the motor 124, Turbine drive control by the wastegate valve 14 , intake air amount control by the throttle valve 13 , and valve operation phase control by the intake valve actuator 201 and the exhaust valve actuator 202 . The required torque TRQD is calculated mainly from the accelerator pedal operation amount AP, and is calculated so as to increase as the accelerator pedal operation amount AP increases.

3 shows a lift curve for explaining the variable range of the valve operating phase realized by the valve operating phase variable mechanism 20, and the horizontal axis is the crankshaft angle CA ("0" corresponds to the top dead center at the beginning of the intake stroke). The dotted lines L1 and L3 correspond to the most advanced action phases of the exhaust valve and the intake valve respectively, and the solid lines L2 and L4 correspond to the most retarded action phases of the exhaust valve and the intake valve respectively. In the present embodiment, the overlap period TCAOVL in which the valve opening period of the intake valve overlaps with the valve opening period of the exhaust valve is an important control parameter. Therefore, the intake valve opening timing CAIO and the exhaust valve closing timing CAEC are used The variable range of TCAOVL during the overlap period will be described.

In the valve action phase variable mechanism 20 of this embodiment, the most advanced phase CAIOMIN of the intake valve opening timing CAIO is about ATDC (after the intake stroke starts at top dead center) -40 degrees (that is, 40 degrees before top dead center) ), the most lagging phase CAIOMAX is about ATDC40 degrees, the most advanced phase CAECMIN of the exhaust valve closing timing CAEC is about ATDC-20 degrees, and the most lagging phase CAECMAX is about ATDC30 degrees. Therefore, when the overlap period TCAOVL is defined as (CAEC-CAIO), the minimum value is a value smaller than 0, and the maximum value TCAOVLMAX is (CAECMAX-CAIOMIN: about 70 degrees).

In addition, in FIG. 3 , a state in which the lift amount LFT is greater than the reference lift amount LFT0 is regarded as the valve open state, and timings for opening and closing the valve are shown.

4 is a graph showing the relationship between the engine speed NE, the intake pressure PB, and the exhaust pressure PEX when the opening degree of the throttle valve 13 is fully opened, and the solid line L11 indicates that the drive assistance by the motor 124 is not performed. (hereinafter referred to as "motor assist") transition of the exhaust pressure PEX, the dotted line L12 shows the transition of the exhaust pressure PEX when the motor assist is performed, and the dotted line L13 shows the intake pressure PB the passage of time. As can be seen from the figure, in the range where the engine speed NE is lower than the limit speed NEB, the exhaust pressure PEX can be made lower than the intake pressure PB by performing motor assist. In a state where the exhaust pressure PEX is lower than the intake pressure PB, the removal of residual gas in the cylinder can be promoted by increasing the overlap period TCAOVL.

Therefore, in the present embodiment, in the operating state (hereinafter referred to as "specific operating state") in which the engine speed NE is low and the intake pressure PB is lower than the target supercharging pressure POBJ, motor assist is performed, and the following motor assist is performed. Auxiliary supercharging control: set the opening degree of the exhaust pressure relief valve 14 to the maximum, reduce the exhaust pressure PEX, and increase the overlap period TCAOVL. The target supercharging pressure POBJ is the target pressure when the intake pressure PB is increased by supercharging, and is set so that the higher the required torque TRQD is, the higher the target supercharging pressure POBJ is. A high-load operating state in which the accelerator pedal is suddenly depressed while the rotational speed NE is low and the throttle valve 13 is opened to a state close to full opening is equivalent.

5 is a timing chart for explaining the outline of the motor assist supercharging control in this embodiment, and (a) to (d) of the drawing show the output torque TRQM of the motor 124 and the output torque of the wastegate valve 14, respectively. The opening degree (hereinafter referred to as "WG opening degree") WGO, the intake pressure PB and the exhaust pressure PEX, and the transition of the intake valve opening timing CAIO and the exhaust valve closing timing CAEC. In addition, the dotted line shown in (b) of FIG. 5 shows the transition of the flow rate of the exhaust gas passing through the wastegate valve 14 . In addition, the vertical axis of (d) of FIG. 5 shows that the intake valve opening timing CAIO and the exhaust valve closing timing CAEC increase as they are retarded.

At time t0, after motor assist supercharging control is started, motor 124 is driven so that motor output torque TRQM becomes maximum value TMAX, and wastegate valve 14 is opened to set WG opening WGO to maximum opening VOMAX. The solid line and the dotted line in (d) of FIG. 5 show the transition of the intake valve opening timing CAIO and the exhaust valve closing timing CAEC, respectively. Immediately after the start of the motor assist supercharging control, the motor assist supercharging control is maintained immediately after the start of the motor assist supercharging control. value at start. The example shown in (d) of FIG. 5 corresponds to a case where the overlap period TCAOVL at the start of the motor assist boost control is smaller than the value "0".

The intake valve opening timing CAIO is advanced from around time t1 when the intake pressure PB exceeds the exhaust pressure PEX, and the valve operation phase is changed so as to retard the exhaust valve closing timing CAEC, and the overlap period TCAOVL increases. (d) of FIG. 5 shows that the change of the valve operating phase starts at time t1, which shows an ideal state, but actually the start time of changing the valve operating phase does not necessarily coincide with time t1.

When the intake pressure PB reaches the target supercharging pressure POBJ at time t2 , transition control is performed to gradually decrease the motor output torque TRQM and the WG opening WGO. At this time, the operation phases of the intake valve and the exhaust valve are controlled such that the intake valve opening timing CAIO is gradually delayed, and the exhaust valve closing timing CAEC is gradually advanced. At time t3, both the motor output torque TRQM and the WG opening WGO become "0", and the normal supercharging control is shifted to. In addition, the intake valve opening timing CAIO is actually changed (advanced, retarded) by changing the intake valve operating phase CAIN, and the exhaust valve closing period CAEC is actually changed by changing the exhaust valve operating phase CAEX. change.

6 is a diagram showing an ideal relationship between the differential pressure DP (=PB-PEX) obtained by subtracting the exhaust pressure PEX from the intake pressure PB and the overlap period TCAOVL. In this embodiment, when the differential pressure DP is negative value, in principle, set the overlap period TCAOVL to a value smaller than "0" to obtain the characteristic that the overlap period TCAOVL increases with the increase of the differential pressure DP, and perform the calculation map of the intake valve action phase CAIN (hereinafter This is referred to as "CAIN map") and the calculation map of exhaust valve operating phase CAEX (hereinafter "CAEX map").

In this embodiment, as shown in FIG. 7 , there are provided a first CAIN map ((a) in the drawing) and a first CAEX map ( This figure (c)), and the 2nd CAIN map (this figure (b)) and the 2nd CAEX map (this figure (d)) corresponding to the state where motor assist is not performed (0%). Each map is set based on the engine speed NE and the estimated output torque TRQH of the engine 1 . The estimated output torque TRQH is calculated from the intake air flow rate GAIR of the engine 1 and the ignition timing IG. More specifically, the estimated output torque TRQH is calculated in such a manner that it increases as the intake air flow rate GAIR increases, when the ignition timing IG is retarded from the optimum ignition timing (ignition timing at which the output torque is maximum), The estimated output torque TRQH is calculated so as to decrease as its delay amount increases.

In the first and second CAIN maps, the advance amounts CAIN0~CAIN5 and CAIN0~CAIN3a based on the most retarded phase are set, and in the first and second CAEX maps, the advance amounts based on the most advanced phase are set. Delays CAEX0~CAEX4 and CAEX0~CAEX3. In addition, both CAIN0 and CAEX0 correspond to the reference phase and are set to "0". Furthermore, when the motor output torque TRQM is between 0% and 100%, an interpolation calculation is performed based on the motor output torque TRQM at that time, thereby calculating the intake valve operation phase CAIN and the exhaust valve operation phase CAEX.

The setting values of the first and second CAIN maps are set to have the following relationship: CAIN0<CAIN1<CAIN2<CAIN3<CAIN3a<CAIN4<CAIN5, that is, in the high load region where the estimated output torque TRQH is large, the first The set value of the 1st CAIN map is larger than the set value of the 2nd CAIN map, and TCAOVL increases during the overlapping period.

In addition, the setting values of the first and second CAEX maps have the following relationship: CAEX0<CAEX1<CAEX2<CAEX3<CAEX4, that is, in the high load region where the estimated output torque TRQH is large, the first CAEX map is set so that The set value of the map is larger than the set value of the second CAEX map, and TCAOVL increases during the overlapping period.

The change characteristics of the intake valve opening timing CAIO and the change characteristics of the exhaust valve closing period CAEC close to the characteristics shown in (d) of FIG. 5 are realized by the map setting shown in FIG. Figure 6 shows the change characteristics of TCAOVL during the overlap period of the ideal characteristics. In addition, in (d) of FIG. 5 , the reason why the intake valve opening timing CAIO and the exhaust valve closing period CAEC are maintained during the period from time t0 to t1 is that, relative to the target supercharging pressure accompanied by an increase in the required torque TRQD The increase of POBJ delays the increase of estimated output torque TRQH.

FIG. 8 is a diagram showing transition of the output torque TRQE when the engine output control corresponding to the requested torque TRQD of the engine 1 is performed. The dotted line L21 of this figure shows the transition of the required torque TRQD, and the solid line L22 and dotted line L23 show the transition of the output torque TRQE. Corresponds to the case of pressure control. As shown in FIG. 8 , by executing the motor assist supercharging control, the engine output torque TRQE can be rapidly increased to the required torque TRQD, and the responsiveness improvement effect of the turbocharger 12 can be obtained.

9 is a timing chart (the horizontal axis is the crankshaft angle CA) for explaining that the period during which the scavenging effect can be obtained by making the intake pressure higher than the exhaust pressure by performing motor assist supercharging control increases. (a) shows the operating phases of the intake valve and the exhaust valve, and (b) of the figure shows transitions of the intake pressure PBS and the exhaust pressure PEXS. Here, the intake pressure PBS and the exhaust pressure PEXS are equivalent to the intake pressure and exhaust pressure of a single cylinder.

The dotted lines L31, L33, L41 and L51 correspond to the case where the motor assist boost control is not performed, and the solid lines L32, L34, L42 and L52 correspond to the case where the motor assist boost control is performed.

When the motor assist supercharging control is not performed, the high intake pressure period in which the intake pressure PBS is higher than the exhaust pressure PEXS is TCA1, and the overlap period TCAOVL in which the scavenging effect can be obtained is limited to the high intake pressure period TCA1 or less. On the other hand, when the motor assist supercharging control is performed, the intake pressure PBS rises from the pressure value indicated by the dotted line L51 to the pressure value indicated by the solid line L52. Therefore, the period of high intake pressure is TCA2, and it is possible to The overlap period TCAOVL in which the purge effect can be obtained is increased to the high intake pressure period TCA2. Note that the transition of the exhaust pressure PEXS changes from the dotted line L41 to the solid line L42 because the exhaust valve operation phase is delayed in order to increase the overlap period TCAOVL.

FIG. 10 is a flowchart for explaining the above-described motor assist supercharging control. In step S11, the target supercharging pressure POBJ is calculated from the requested torque TRQD and the engine speed NE. In step S12, it is judged whether or not the engine speed NE is lower than the limit speed NEB (for example, set to about 3000 rpm). When the answer in step S12 is affirmative ("Yes"), it is judged whether or not the intake pressure PB is higher than the target supercharging pressure POBJ (step S13). The boundary speed NEB is set so as to be able to determine the low speed state of the engine 1 in which the exhaust pressure PEX is made lower than the intake pressure PB by performing motor assist (see FIG. 4 ).

When the answer of step S12 or S13 is negative ("No") and the engine speed NE is above the limit speed NEB, or the intake pressure PB is above the target supercharging pressure POBJ, check whether the motor assist ON flag FMAST is "1". Discrimination (step S18). The motor assist ON flag FMAST is set to "1" when the motor assist is started (see step S14). When the answer in step S18 is negative ("No"), the motor assist is set to "OFF" (step S19), the intake valve operating phase CAIN is calculated using the second CAIN map (step S20), and the second CAEX map is used to calculate the exhaust valve operating phase CAEX (step S21). Then, normal supercharging pressure control is performed (step S25). If the answer of step S18 is affirmative ("Yes"), and the answer of step S12 or S13 is negative ("No") after execution of step S14, the process proceeds to step S22, and the transitional control described with reference to FIG. 5 is executed.

When the answer at step S13 is affirmative ("Yes"), motor assist supercharging pressure control is executed. In step S14, the motor assist is set to "ON", and the motor assist ON flag FMAST is set to "1". At this time, the motor 124 is driven such that the output torque TRQM becomes the maximum value TMAX. In step S15, the wastegate valve 14 is fully opened. That is, when the wastegate valve 14 is closed, the wastegate valve 14 is opened to the fully open state, and when the wastegate valve 14 is already in the fully open state, the state is maintained.

In step S16, the intake valve operating phase CAIN is calculated using the first CAIN map (step S16), and the exhaust valve operating phase CAEX is calculated using the first CAEX map (step S17). As described with reference to FIG. 7 , in the high-load region where the estimated output torque TRQH is large, the setting value of the first CAIN map is larger than the setting value of the second CAIN map, and the setting value of the first CAEX map is larger than that of the second CAIN map. The setting value of the 2nd CAEX map. Therefore, the overlap period TCAOVL is increased by applying the intake valve operation phase CAIN and the exhaust valve operation phase CAEX calculated in steps S16 and S17. After step S17 is executed, return to step S12.

During the execution of the motor assist supercharging control according to steps S12 to S17, if the answer of step S12 or S13 is negative (“No”), the process proceeds to step S22 via step S18, and the transient control described with reference to FIG. 5 is executed. . That is, the motor output torque TRQM and the WG opening WGO are gradually decreased. In addition, the intake valve operating phase CAIN is calculated by interpolating the set value of the first CAIN map and the set value of the second CAIN map, and the intake valve operating phase CAIN is gradually delayed. The exhaust valve operation phase CAEX is calculated by interpolation calculation of the set value of the 1st CAEX map and the set value of the 2nd CAEX map, and the exhaust valve operation phase CAEX is gradually advanced.

In step S23, it is judged whether or not the motor output torque TRQM is "0", and if the answer is negative ("No"), the transient control is continued. When the answer in step S23 is affirmative ("Yes"), the motor assist ON flag FMAST is set to "0" (step S24), and the process shifts to normal control.

As described above, in the present embodiment, when executing the motor-assisted supercharging control in which the motor 124 assists the drive of the compressor 123, control is performed such that the opening degree WGO of the wastegate valve 14 is increased and the opening degree WGO of the wastegate valve 14 is increased. The overlap period TCAOVL in which the valve opening period of the intake valve overlaps with the valve opening period of the exhaust valve. By increasing the opening degree WGO of the wastegate valve 14, when the required load TRQD is high, that is, the target boost pressure POBJ is high, the increase in the exhaust pressure PEX can be minimized, the charging efficiency can be improved, and the ignition timing can be set. Set to be close to optimum ignition timing. In addition, by increasing the overlap period TCAOVL, it is possible to promote the removal of residual gas in the combustion chamber, increase the amount of fresh air, avoid knocking, and advance the ignition timing. As a result, engine output can be increased and fuel efficiency can be improved. More specifically, by performing motor assist supercharging control in a specific operating state (NE<NEB, PB<POBJ) of the engine 1, the effect of increasing the engine output and improving The effect of the responsiveness of the turbocharger 12 .

Also, when the intake pressure PBA reaches the target supercharging pressure POBJ after the start of the motor assist, the motor output torque TRQM is reduced, and transition control is performed to reduce the opening degree WGO of the wastegate valve. After a sufficient supercharging pressure (target supercharging pressure) is obtained, the motor output torque TRQM is reduced to shift to supercharging using normal exhaust energy, thereby reducing the electric power for driving the motor 124 .

In addition, the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the control shown in FIG. 10 , the specific operating state in which the motor assist supercharging control is executed is a state in which the engine speed NE is lower than the boundary speed NEB and the intake pressure PB is lower than the target supercharging pressure POBJ. Conveniently, it is also possible to determine the specific operating state from the time when the accelerator pedal operation amount AP suddenly increases from a small value to the elapse of a predetermined time TMASTX, and execute the motor assist supercharging control. The predetermined time TMASTX is set such that the intake pressure PB reliably reaches the target supercharging pressure starting from the time when the throttle valve opening changes from a nearly fully closed state to a fully open throttle operation (motor assist supercharging control start time). Time for POBJs. By setting the predetermined time TMASTX so that a sufficient supercharging pressure can be obtained, excessive assist by the motor 124 can be avoided, and power consumption can be reduced.

In addition, in the example shown in FIG. 5( d ), an operation example in which the overlap period TCAOVL at the start time of the motor assist supercharging control is a value smaller than "0" and the overlap period TCAOVL is increased from this state is shown, However, there is also a case where the overlap period TCAOVL at the start time of the motor assist supercharging control is an initial value greater than "0". Control during TCAOVL increase.

In addition, in the above-mentioned motor assist supercharging control, the motor output torque TRQM and the WG opening WGO are set to the maximum values from the control start time, but they are not necessarily the maximum values, and may be set to be slightly smaller than the maximum values. value. In addition, in the above-mentioned embodiment, the valve operating phase variable mechanism 20 capable of changing the operating phase of the intake valve and the exhaust valve is used, but it can be achieved by changing the operating phase of either the intake valve or the exhaust valve. Since the overlap period TCAOVL is changed, a valve operation phase variable mechanism capable of changing the operation phase of either the intake valve or the exhaust valve may be used as the valve operation phase variable mechanism 20 . Furthermore, FIG. 1 shows a four-cylinder engine, but the invention can be applied regardless of the number of cylinders.

Claims (4)

1. A control device for an internal combustion engine, which is an internal combustion engine in which fuel is directly injected into a combustion chamber, and the control device has: A supercharger having: a turbine provided in an exhaust passage of the internal combustion engine; a compressor rotationally driven by the turbine to pressurize intake air of the internal combustion engine; and an electric motor provided capable of driving the compressor; a valve operation phase variable mechanism capable of changing an operation phase of at least one of an intake valve and an exhaust valve of the internal combustion engine; and a wastegate disposed in a bypass passage bypassing the turbine, The control device of the internal combustion engine is characterized in that, When the compressor is driven and assisted by the electric motor, the opening degree of the exhaust pressure relief valve is increased, and the valve opening period of the intake valve overlaps with the valve opening period of the exhaust valve period of overlap. 2. The control device for an internal combustion engine according to claim 1, wherein: The drive assist by the electric motor is performed in an operating state in which the rotation speed of the internal combustion engine is low and the intake pressure of the internal combustion engine is lower than a target supercharging pressure. 3. The control device for an internal combustion engine according to claim 1 or 2, wherein: After the start of the drive assist by the electric motor, when the intake pressure of the internal combustion engine reaches a target supercharging pressure, the output of the electric motor is reduced and the opening degree of the wastegate valve is reduced. 4. The control device for an internal combustion engine according to claim 1 or 2, wherein: When a predetermined time elapses from the start of the drive assistance by the electric motor, the output of the electric motor is reduced to reduce the opening degree of the wastegate valve.